U.S. Pat. Nos. 5,410,728 and 5,509,004 both assigned to the assignee of the present invention describe a communication network that incorporates both space-based network switching centers and ground-based network switching centers to provide reasonable service quality with both basic and supplementary communication services. Satellite configurations for satellite cellular telephone communication systems are shown in those patents. In those configurations, a number of satellites in Low Earth Orbit ("LEO") are utilized. The satellites are in continuous movement about Earth. The satellite cellular structures are somewhat analogous to the present day cellular mobile telephone systems. In cellular mobile systems, cellular sites are fixed and users are mobile. As a user travels from one cell site to another, the telephone call is handed off from one cellular switching unit to another. In the satellite system of the '728 and '004 patents, users are relatively fixed at any given time while the satellites, which are the cells, are i n continuous movement. With a hand-held or mobile mounted cellular telephone, connection to one of the satellites is made directly from the hand-held mobile mounted or remotely fixed telephone to one of the nearest satellite switches. As a satellite which originally acted as a switching unit for a particular user leaves a cell of that switch, the user's call is "handed off" to the appropriate adjacent cell. Adjacent cells may be cells within one satellite or cells of other satellites located either in a particular orbiting plane or an adjacent orbiting plane. User's may "roam" but this roaming distance is relatively small compared to the traveling distance of the satellite switches.
Similar to the cellular mobile telephone system, the satellite cellular communication system provides spectral efficiency. This means that the same frequency may be simultaneously used by different satellite switches.
Spectral efficiency is provided by the spacial diversity between satellite switches and users. The users may be located anywhere on a land mass, on the water, or in the air at an altitude less than that of the LEO satellites. For example, a person at one location on earth could call a person at another location on earth, a person on a boat, or a person in an aircraft.
The previously described system provides a communication network which incorporates both space-based network switching centers and ground-based network switching centers to provide reasonable service quality for both basic and supplementary communication services. To establish telephone calls in a system of this type requires the use of ground-based switching networks. Various regulatory agencies may be involved in developing tariffs for service utilizing such a cellular system. In addition, the routing of telephone calls through the Public Switching Telephone Network ("PSTN") results in so-called "tail fees" for each call.